/Engine/Plugins/NetcodeUnitTest/NetcodeUnitTest/Source/NetcodeUnitTest/Classes/NUTActor.h
Send a 'ping' RPC to all clients, to make them log a ping, which unit tests then use to verify the presence of a client process
[UFUNCTION](Programming/UnrealArchitecture/Reference/Functions)(Reliable, Server, WithValidation) void ServerClientPing()